The present invention relates to a stent that is implanted in lumens of an organism such as the blood vessel, the bile duct, the trachea, the esophagus, the ureter, and the like to improve a stenosed portion or a closed portion generated in the lumens. The present invention also relates to a stent delivery device.
To cure various diseases that are caused when the blood vessel or lumens are stenosed or closed, the stent which is a tubular medical appliance is implanted at the stenosed portion or the closed portion to expand them and secure the lumen thereof.
Because the stent is inserted into the body from the outside, its diameter is small. The stent is expanded to make its diameter large at the stenosed portion or the closed portion to keep the expanded state of the lumen thereof.
The stent is cylindrical and made of a metal wire or a processed metal pipe. After the stent is mounted on a catheter or the like by decreasing its diameter, it is inserted into the body. Thereafter the stent is expanded at a desired portion by using an expanding method and fixed to an inner wall of the lumen of the desired portion, with the stent in close contact therewith to maintain the configuration of the lumen. The stent is classified into a self-expandable stent and a balloon expandable stent in dependence on the function thereof and an implantation method. The balloon expandable stent which itself has no expanding function is secured at a desired portion. Then, a balloon provided in the stent is inflated to expand (plastically deform) the stent by an expansive force of the balloon so that the stent is brought into close contact with the inner surface of the desired lumen. It is necessary to perform an operation of expanding the stent of this type in implanting it to the desired portion of the organism.
The balloon expandable stent is mostly used as the stent to be used to cure blood vessels and particularly the coronary arteries. The stent is demanded to have an axially flexible construction to cope with a lot of cases.
The balloon expandable stent is classified into a closed cell type and an opened cell type in dependence on the configuration of a stratum thereof. The balloon expandable stent of the opened cell type has an advantage that it is flexible. Thus the balloon expandable stent of the opened cell type is favorably implanted in a desired portion because it is capable of flexibly following a travel direction of a blood vessel and its configuration. Thereby it is possible to prevent the blood vessel from being stimulated. But the balloon expandable stent of the opened cell type has a disadvantage that the stratum thereof flares outward. On the other hand, the balloon expandable stent of the closed cell type has an advantage that the stratum thereof does not flare outward, but is incapable of flexibly following the travel direction of the blood vessel and its configuration. The balloon expandable stent of the opened cell type and the closed cell type have both the advantage and the disadvantage. Thus it is necessary to use the balloon expandable stent of the opened cell type or the closed cell type in dependence on the travel direction and configuration of the blood vessel.
The balloon expandable stent of the opened cell type is proposed by the present applicant and disclosed in JPA No. 2002-136601.
The balloon expandable stent of the opened cell type disclosed in JPA No. 2002-136601 has a sufficient expanded state retention force owing to the opened cell portion thereof. But it is desirable that the stent has a higher expanded state retention force. It is also desirable that it has a higher follow-up performance for the configurations of organs of the organism.